rmi 问题 Connection refused to host，急！

大侠们，我遇到一个rmi客户端异常问题，帮忙看一下：ComputeEngine_Stub[UnicastRef [liveRef: [endpoint:[127.0.0.1:1987](remote),objID:[f7f6b2a:120f0ddc142:-8000, 0]]]]
java.rmi.ConnectException: Connection refused to host: 127.0.0.1; nested exception is: 
java.net.ConnectException: Connection refused: connect
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:574)
at sun.rmi.transport.tcp.TCPChannel.createConnection(TCPChannel.java:185)
at sun.rmi.transport.tcp.TCPChannel.newConnection(TCPChannel.java:171)
at sun.rmi.server.UnicastRef.invoke(UnicastRef.java:94)
at com.ls.rmiservice.sample.ComputeEngine_Stub.executeTask(Unknown Source)
at com.ls.client.sample.ComputePi.main(ComputePi.java:28)
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:519)
at java.net.Socket.connect(Socket.java:469)
at java.net.Socket.<init>(Socket.java:366)
at java.net.Socket.<init>(Socket.java:179)
at sun.rmi.transport.proxy.RMIDirectSocketFactory.createSocket(RMIDirectSocketFactory.java:22)
at sun.rmi.transport.proxy.RMIMasterSocketFactory.createSocket(RMIMasterSocketFactory.java:128)
at sun.rmi.transport.tcp.TCPEndpoint.newSocket(TCPEndpoint.java:569)
... 5 more服务器端已经启动了，并且绑定了服务。客户端程序请求服务时，registry.lookup("....");执行没有问题，并且拿回了对象，打印如：
ComputeEngine_Stub[UnicastRef [liveRef: [endpoint:[127.0.0.1:1987](remote),objID:[f7f6b2a:120f0ddc142:-8000, 0]]]]之后，调用返回对象的方法，就抛了上述异常。请问怎么解决呀？谢谢。